Professor Anthony Glees told the paper that "These files show there was contact between Corbyn and a Czech intelligence official, even if he did not know it." Yet this would have been true of many MPs of all parties who had contacts with East European diplomats. Indeed, the expansion of such contacts would have been one manifestation of perestroika in what was the early Gorbachev era.

Veteran investigative journalist David Leigh has said of the story, based on Czech intelligence files: ' I would guess this is just about as credible as a Sun expenses claim for 'lunch with contact'.

Leigh ought to know. His 1988 book, The Wilson Plot, documents the long running vendetta of a coterie of British intelligence officers against Labour Prime Minister Harold Wilson. One key source of anti-Labour smears was material provided by former Czech intelligence officer Josef Frolik.

I discussed Frolik here last year, in the context of his allegations about a gay honeytrap operation against Edward Heath, which seem to have been taken seriously by MI5, much to Heath's chagrin.

Frolik also named a string of Labour MPs as Czech contacts following his defection in 1969. This turned out to include one genuine, if low-level, agent, Will Owen, and one likely British double-agent, Tom Driberg, but for the most part, the significance of such contacts was highly questionable.

As Frolik himself describes it, his colleagues vied with each other to boast how successful they were. He also mentions how unscrupulous this process of amassing 'informants' could be: He says one of his more gorilla-like colleagues in London constantly treated them all to expenses-paid sessions in London night-clubs - 'Jan Koska had invented an "English policeman" who cost Prague £1,00 in bribes to cover Koska's drinking bills.' (Leigh, The Wilson Plot, 1988, p.168).

Frolik's MI5 handler Charles Elwell subsequently became a right-wing activist known among other things for labelling the future Archbishop of Canterbury Rowan Williams as a subversive. Such episodes are perhaps a salutary reminder that it didn't take the internet to bring smears and conspiracy theories into mainsteam politics.